does it have the skinny 1 3/4" brake shoes and drums?
if so step up to the large brake offset on the axle and run the b-body brake while you swaping it around to 5 on 4.5 wbp,
as for the suregrip jack both wheels up and have a buddy grab one side and turn it while you grab the other and spin in diff direction..if you can slip it in needs replaced
if its the cone type,there are shims to use after milling some off the cones to make the differance back up on the side gears which can be done to get some more life out of it faily cheap,contact..Trwaters here on the board for the shims,they are 30$ a pr and come with instructions
doctor diff a member on the board here can set you up with the axle package also
moser also has the large brake offset axles wit 5 on 4.5 wbp 299.00$ apair with green bearings
green bearing will get rid of the end play adjustment unless you would prefer to keep the stock bearing set and adjuster
geens and larger brake off set will make the whole rear end 1/2" wider..1/4" each side also
and a 4 1/2" backset on the rims works just right for it on the a-body
i would try a local spring/axle shop to redo the chunk ans save shipping it
and its a suregrip in there..posi dont go round here!saavay?
doctordiff is a good bet of parts and service
